U.S. patent application number 17/190398 was filed with the patent office on 2021-11-25 for organic electroluminescent device.
The applicant listed for this patent is Solus Advanced Materials Co., Ltd.. Invention is credited to Songie HAN, Taehyung KIM, Jonghun MOON, Hocheol PARK.
Application Number | 20210367178 17/190398 |
Document ID | / |
Family ID | 1000005443484 |
Filed Date | 2021-11-25 |
United States Patent
Application |
20210367178 |
Kind Code |
A1 |
MOON; Jonghun ; et
al. |
November 25, 2021 |
ORGANIC ELECTROLUMINESCENT DEVICE
Abstract
The present invention provides an organic electroluminescent
device including an electron-leakage suppression layer and a
hole-leakage suppression layer adjusted to have predetermined
physical properties, in portions of a hole transporting area and an
electron transporting area disposed on opposite sides of a light
emitting layer, respectively, thereby reducing leakage of electrons
and holes and thus improved in terms of characteristics such as a
low driving voltage, high luminous efficiency, and long
lifespan.
Inventors: |
MOON; Jonghun; (Yongin,
KR) ; KIM; Taehyung; (Yongin, KR) ; PARK;
Hocheol; (Yongin, KR) ; HAN; Songie; (Yongin,
KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Solus Advanced Materials Co., Ltd. |
lksan |
|
KR |
|
|
Family ID: |
1000005443484 |
Appl. No.: |
17/190398 |
Filed: |
March 3, 2021 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 51/508 20130101;
H01L 51/5004 20130101; H01L 51/5092 20130101; H01L 51/5064
20130101 |
International
Class: |
H01L 51/50 20060101
H01L051/50 |
Foreign Application Data
Date |
Code |
Application Number |
May 12, 2020 |
KR |
10-2020-0056397 |
Claims
1. An organic electroluminescent device comprising: a structure in
which an anode; a hole transporting area; a light emitting layer;
an electron transporting area, and a cathode are sequentially
stacked, wherein the light emitting layer includes a host, each of
the hole transporting area and the electron transporting area
comprises at least two layers, one of the at least two layers of
the hole transporting area contacting the light emitting layer is
an electron-leakage suppression layer E-LSL, one of the at least
two layers of the electron transporting area contacting the light
emitting layer is a hole-leakage suppression layer H-LSL, a density
of states of HOMO DOS.sub.HOMO and a density of states of LUMO
DOS.sub.LUMO of each of the electron-leakage suppression layer
E-LSL and the hole-leakage suppression layer H-LSL satisfy at least
one of the following conditions (i) and (ii): (i) with respect to
the density of states of LUMO, a density of states of LUMO
DOS.sub.LUMO.sup.HOST of the host overlaps the density of states of
LUMO DOS.sub.LUMO.sup.H-LSL of the hole-leakage suppression layer
H-LSL and does not overlap the density of states of LUMO
DOS.sub.LUMO.sup.E-LSL of the electron-leakage suppression layer
E-LSL, and (ii) with respect to the density of states of HOMO, a
density of states of HOMO DOS.sub.HOMO.sup.HOST of the host
overlaps the density of states of HOMO DOS.sub.HOMO.sup.E-LSL of
the electron-leakage suppression layer E-LSL and does not overlap
the density of states of HOMO DOS.sub.HOMO.sup.H-LSL of the
hole-leakage suppression layer H-LSL.
2. The organic electroluminescent device of claim 1, wherein the
densities of states of LUMO DOS.sub.LUMO of the electron-leakage
suppression layer E-LSL and the hole-leakage suppression layer
H-LSL satisfy the condition (i), and the densities of states of
HOMO DOS.sub.HOMO of the electron-leakage suppression layer E-LSL
and the hole-leakage suppression layer H-LSL satisfy the condition
(ii).
3. The organic electroluminescent device of claim 1, wherein with
respect to the density of states of LUMO DOS.sub.LUMO, an overlap
ratio between the density of states of LUMO DOS.sub.LUMO.sup.HOST
of the host and the density of states of LUMO
DOS.sub.LUMO.sup.H-LSL of the hole-leakage suppression layer H-LSL
is more than 0% and 95% or less.
4. The organic electroluminescent device of claim 1, wherein with
respect to the density of states of HOMO DOS.sub.HOMO, an overlap
ratio between the density of states of HOMO DOS.sub.HOMO.sup.HOST
of the host and the density of states of HOMO
DOS.sub.HOMO.sup.E-LSL of the electron-leakage suppression layer
E-LSL is more than 0% and 95% or less.
5. The organic electroluminescent device of claim 1, wherein with
respect to an absolute value of the density of states of LUMO
DOS.sub.LUMO, a difference between a minimum LUMO energy value of
the density of states of LUMO DOS.sub.LUMO.sup.HOST of the host and
a maximum LUMO energy value of the density of states of LUMO
DOS.sub.LUMO.sup.E-LSL of the electron-leakage suppression layer
E-LSL that do not overlap each other is more than 0 eV and 2 eV or
less.
6. The organic electroluminescent device of claim 1, wherein with
respect to an absolute value of the density of states of HOMO
DOS.sub.HOMO, a difference between a maximum HOMO energy value of
the density of states of HOMO DOS.sub.HOMO.sup.HOST of the host and
a minimum HOMO energy value of the density of states of HOMO
DOS.sub.HOMO.sup.H-LSL of the hole-leakage suppression layer H-LSL
that do not overlap each other is more than 0 eV and 2 eV or
less.
7. The organic electroluminescent device of claim 1, wherein the
hole transporting area comprises at least one of an
electron-leakage suppression layer, a hole transporting layer and a
hole injection layer.
8. The organic electroluminescent device of claim 7, wherein with
respect to the light emitting layer, the hole transporting area has
a structure in which the electron-leakage suppression layer and the
hole injection layer are disposed, or a structure in which the
electron-leakage suppression layer, the hole transporting layer,
and the hole injection layer are disposed.
9. The organic electroluminescent device of claim 1, wherein the
electron transporting area comprises at least one of a hole-leakage
suppression layer, an electron transporting layer, and an electron
injection layer.
10. The organic electroluminescent device of claim 9, wherein with
respect to the light emitting layer, the electron transporting area
has a structure in which the hole-leakage suppression layer and the
electron injection layer are disposed, or a structure in which the
hole-leakage suppression layer, the electron transporting layer,
and the electron injection layer are disposed.
11. The organic electroluminescent device of claim 1, wherein an
absolute value difference .DELTA.LUMO between a LUMO energy level
of the electron-leakage suppression layer E-LSL and a LUMO energy
level of the host is 2.0 eV or less.
12. The organic electroluminescent device of claim 1, wherein an
absolute value difference .DELTA.HOMO between a HOMO energy level
of the electron-leakage suppression layer E-LSL and a HOMO energy
level of the host is 2.0 eV or less.
13. The organic electroluminescent device of claim 1, wherein an
absolute value difference .DELTA.LUMO between a LUMO energy level
of the hole-leakage suppression layer H-LSL and a LUMO energy level
of the host is 2.0 eV or less.
14. The organic electroluminescent device of claim 1, wherein an
absolute value difference .DELTA.HOMO between a HOMO energy level
of the hole-leakage suppression layer H-LSL and a HOMO energy level
of the host is 2.0 eV or less.
15. The organic electroluminescent device of claim 1, wherein a
triplet energy T1 of each of the electron-leakage suppression layer
E-LSL and the hole-leakage suppression layer H-LSL is 1.5 eV or
more.
16. The organic electroluminescent device of claim 1, wherein a
singlet energy S1 of each of the electron-leakage suppression layer
E-LSL and the hole-leakage suppression layer H-LSL is 2.0 eV or
more.
17. The organic electroluminescent device of claim 1, wherein an
absolute value of a HOMO energy of each of the electron-leakage
suppression layer E-LSL and the hole-leakage suppression layer
H-LSL is 4.5 eV or more.
18. The organic electroluminescent device of claim 1, wherein an
absolute value of a LUMO energy of each of the electron-leakage
suppression layer E-LSL and the hole-leakage suppression layer
H-LSL is 1.0 eV or more.
19. The organic electroluminescent device of claim 1, wherein a
lowest energy level of bond dissociation energy BDE of each of the
electron-leakage suppression layer E-LSL and the hole-leakage
suppression layer H-LSL in a ground state is 1.00 eV or more.
20. The organic electroluminescent device of claim 1, wherein each
of the electron-leakage suppression layer E-LSL and the
hole-leakage suppression layer H-LSL has a refractive index n of
0.6 or more in a blue wavelength area ranging from 400 to 470 nm;
or a dipole moment of each of the electron-leakage suppression
layer E-LSL and the hole-leakage suppression layer H-LSL is more
than 0.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims priority to and the benefit of
Korean Patent Application No. 10-2020-0056397, filed on May 12,
2020, in the Korean Intellectual Property Office (KIPO), the entire
content of which is incorporated herein by reference.
TECHNICAL FIELD
[0002] The present invention relates to an organic
electroluminescent device ("EL device") including an
electron-leakage suppression layer E-LSL and a hole-leakage
suppression layer H-LSL adjusted to have predetermined physical
properties, in portions of a hole transporting area and an electron
transporting area disposed on opposite sides of a light emitting
layer, respectively, thereby reducing leakage of electrons and
holes and thus improved in terms of characteristics such as a low
driving voltage, high luminous efficiency, and long lifespan.
DISCUSSION OF RELATED ART
[0003] In 1965, studies on organic EL devices led to blue
electroluminescence which uses anthracene monocrystals, and in
1987, Tang suggested an organic EL device in a two-layered stack
structure which includes a hole layer (NPB) and a light emitting
layer (Alq.sub.3). Afterwards, in order to realize high efficiency
and long life characteristics required for commercialization of
organic EL devices, a multilayer stack structure that includes, for
example, organic layers responsible for hole injection and
transporting, organic layers responsible for electron injection and
transporting, and an organic layer responsible for inducing
combination of the holes and electrons to cause
electroluminescence, each having distinctive and subdivided
functions, has been suggested. The introduction of the multilayer
stack structure improved the performance of the organic EL devices
up to the level of commercialization, and such a multilayer stack
structure has been expanding its application range from portable
radio display products in 1997 to portable information display
devices and TV display devices.
[0004] The demand for larger displays and higher resolutions has
led to challenges, for example, high efficiency and long lifespan,
for the organic EL devices. Particularly, the high resolution that
may be realized by forming more pixels in the same area results in
a decrease in a light emitting area of an organic EL pixel, thus
inevitably reducing the lifespan, which has become one of the most
important technical challenges to overcome for the organic EL
device.
[0005] In the organic EL device, when current or voltage is applied
to two electrodes, holes are injected into an organic layer at an
anode, and electrons are injected into the organic layer at a
cathode. When the injected holes and electrons meet, an exciton is
formed, and the exciton falls to the ground state, resulting in
light emission. Such organic EL devices may be classified,
according to an electron spin type of the formed excitons, into
fluorescent EL devices in which singlet excitons contribute to
light emission and phosphorescent EL devices in which triplet
excitons contribute to light emission.
[0006] In terms of the electron spin of the excitons that are
formed by recombination of electrons and holes, 25% of singlet
excitons and 75% of triplet excitons are produced. In the
fluorescent EL devices which emit light by singlet excitons, the
internal quantum efficiency may not theoretically exceed 25%
depending on the production ratio, and the external quantum
efficiency is regarded to have a limitation of 5%. The
phosphorescent EL devices which emit light by triplet excitons may
improve luminous efficiency by up to four times as compared to
fluorescence, when metal complex compounds containing transition
metal heavy atoms such as Ir and Pt are used as phosphorescent
dopants.
[0007] As described above, although the phosphorescent EL devices
exhibit higher efficiency than fluorescence in terms of luminous
efficiency based on the theoretical fact, in the case of blue
phosphorescent devices, except green and red, the development level
for phosphorescent dopants having deep blue color purity and high
efficiency and hosts having a broad energy gap to satisfy such
phosphorescent dopants is insufficient, and thus blue
phosphorescent devices have not been commercialized yet, and blue
fluorescent devices have been used in products.
[0008] In order to improve such characteristics of the organic EL
device, research results to increase the stability of the organic
EL device by preventing diffusion of holes into an electron
transferring layer have been reported. However, to date, no
satisfactory result has been obtained.
DETAILED DESCRIPTION OF THE INVENTION
Technical Objectives
[0009] The present invention is directed to an organic EL device in
which an electron-leakage suppression layer E-LSL and a
hole-leakage suppression layer H-LSL adjusted in terms of
predetermined physical properties such as a highest occupied
molecular orbital ("HOMO") density of states HOMO-DOS and a lowest
unoccupied molecular orbital ("LUMO") density of states LUMO-DOS
into predetermine ranges are disposed adjacently on opposite sides
of a light emitting layer of the organic EL device, thereby
achieving high efficiency, low voltage and long lifespan.
[0010] Other objects and advantages of the present invention will
be more clearly described by the following detailed description and
claims.
Technical Solution to the Problem
[0011] Aspects of embodiments of the present invention are directed
to an organic electroluminescent device including: a structure in
which an anode; a hole transporting area; a light emitting layer;
an electron transporting area, and a cathode are sequentially
stacked, wherein the light emitting layer includes a host, each of
the hole transporting area and the electron transporting area
includes at least two layers, one of the at least two layers of the
hole transporting area contacting the light emitting layer is an
electron-leakage suppression layer E-LSL, one of the at least two
layers of the electron transporting area contacting the light
emitting layer is a hole-leakage suppression layer H-LSL, a density
of states of HOMO DOS.sub.HOMO and a density of states of LUMO
DOS.sub.LUMO of each of the electron-leakage suppression layer
E-LSL and the hole-leakage suppression layer H-LSL satisfy at least
one of the following conditions (i) and (ii): [0012] (i) with
respect to the density of states of LUMO, a density of states of
LUMO DOS.sub.LUMO.sup.HOST of the host overlaps the density of
states of LUMO DOS.sub.LUMO.sup.H-LSL of the hole-leakage
suppression layer H-LSL and does not overlap the density of states
of LUMO DOS.sub.LUMO.sup.E-LSL of the electron-leakage suppression
layer E-LSL, and [0013] (ii) with respect to the density of states
of HOMO, a density of states of HOMO DOS.sub.HOMO.sup.HOST of the
host overlaps the density of states of HOMO DOS.sub.HOMO.sup.E-LSL
of the electron-leakage suppression layer E-LSL and does not
overlap the density of states of HOMO DOS.sub.HOMO.sup.H-LSL of the
hole-leakage suppression layer H-LSL.
[0014] In some embodiments, the densities of states of LUMO
DOS.sub.LUMO of the electron-leakage suppression layer E-LSL and
the hole-leakage suppression layer H-LSL satisfy the condition (i),
and, the densities of states of HOMO DOS.sub.HOMO of the
electron-leakage suppression layer E-LSL and the hole-leakage
suppression layer H-LSL satisfy the condition (ii).
[0015] In some embodiments, with respect to the density of states
of LUMO DOS.sub.LUMO, an overlap ratio between the density of
states of LUMO DOS.sub.LUMO.sup.HOST of the host and the density of
states of LUMO DOS.sub.LUMO.sup.H-LSL of the hole-leakage
suppression layer H-LSL is more than 0% and 95% or less.
[0016] In some embodiments, with respect to the density of states
of HOMO DOS.sub.HOMO, an overlap ratio between the density of
states of HOMO DOS.sub.HOMO.sup.HOST of the host and the density of
states of HOMO DOS.sub.HOMO.sup.E-LSL of the electron-leakage
suppression layer E-LSL is more than 0% and 95% or less.
[0017] In some embodiments, with respect to an absolute value of
the density of states of LUMO DOS.sub.LUMO, a difference between a
minimum LUMO energy value of the density of states of LUMO
DOS.sub.LUMO.sup.HOST of the host and a maximum LUMO energy value
of the density of states of LUMO DOS.sub.LUMO.sup.E-LSL of the
electron-leakage suppression layer E-LSL that do not overlap each
other is more than 0 eV and 2 eV or less.
[0018] In some embodiments, with respect to an absolute value of
the density of states of HOMO DOS.sub.HOMO, a difference between a
maximum HOMO energy value of the density of states of HOMO
DOS.sub.HOMO.sup.HOST of the host and a minimum HOMO energy value
of the density of states of HOMO DOS.sub.HOMO.sup.H-LSL of the
hole-leakage suppression layer H-LSL that do not overlap each other
is more than 0 eV and 2 eV or less.
[0019] In some embodiments, the hole transporting area may include
at least one of an electron-leakage suppression layer, a hole
transporting layer and a hole injection layer.
[0020] In some embodiments, with respect to the light emitting
layer, the hole transporting area may have a structure in which the
electron-leakage suppression layer and the hole injection layer are
disposed, or a structure in which the electron-leakage suppression
layer, the hole transporting layer, and the hole injection layer
are disposed.
[0021] In some embodiments, the electron transporting area may
include at least one of a hole-leakage suppression layer, an
electron transporting layer, and an electron injection layer.
[0022] In some embodiments, with respect to the light emitting
layer, the electron transporting area may have a structure in which
the hole-leakage suppression layer and the electron injection layer
are disposed, or a structure in which the hole-leakage suppression
layer, the electron transporting layer, and the electron injection
layer are disposed.
[0023] In some embodiments, an absolute value difference
.DELTA.LUMO between a LUMO energy level of the electron-leakage
suppression layer E-LSL and a LUMO energy level of the host may be
2.0 eV or less.
[0024] In some embodiments, an absolute value difference
.DELTA.HOMO between a HOMO energy level of the electron-leakage
suppression layer E-LSL and a HOMO energy level of the host may be
2.0 eV or less.
[0025] In some embodiments, an absolute value difference
.DELTA.LUMO between a LUMO energy level of the hole-leakage
suppression layer H-LSL and a LUMO energy level of the host may be
2.0 eV or less.
[0026] In some embodiments, an absolute value difference
.DELTA.HOMO between a HOMO energy level of the hole-leakage
suppression layer H-LSL and a HOMO energy level of the host may be
2.0 eV or less.
[0027] In some embodiments, a triplet energy T1 of each of the
electron-leakage suppression layer E-LSL and the hole-leakage
suppression layer H-LSL may be 1.5 eV or more.
[0028] In some embodiments, a singlet energy S1 of each of the
electron-leakage suppression layer E-LSL and the hole-leakage
suppression layer H-LSL may be 2.0 eV or more.
[0029] In some embodiments, an absolute value of a HOMO energy of
each of the electron-leakage suppression layer E-LSL and the
hole-leakage suppression layer H-LSL may be 4.5 eV or more.
[0030] In some embodiments, an absolute value of a LUMO energy of
each of the electron-leakage suppression layer E-LSL and the
hole-leakage suppression layer H-LSL may be 1.0 eV or more.
[0031] In some embodiments, a lowest energy level of bond
dissociation energy BDE of each of the electron-leakage suppression
layer E-LSL and the hole-leakage suppression layer H-LSL in a
ground state may be 1.00 eV or more.
[0032] In some embodiments, each of the electron-leakage
suppression layer E-LSL and the hole-leakage suppression layer
H-LSL may have a refractive index n of 0.6 or more in a blue
wavelength area ranging from 400 to 470 nm.
[0033] In some embodiments, a dipole moment of each of the
electron-leakage suppression layer E-LSL and the hole-leakage
suppression layer H-LSL may be more than 0.
[0034] In some embodiments, the light emitting layer includes the
host and a dopant, and a mixing ratio between the host and the
dopant may be 70-99.5:0.5-30 by weight.
[0035] In some embodiments, the light emitting layer may include at
least one selected from the group consisting of green, red, and
blue hosts.
[0036] In some embodiments, the organic electroluminescent device
may include a plurality of light emitting layer stacks including at
least one light emitting layer.
Effects of the Invention
[0037] According to one or more embodiments of the present
invention, an organic EL device may have high efficiency, low
voltage and long lifespan through suppression of electron/hole
leakage, by adopting materials adjusted in terms of, for example, a
HOMO density of states HOMO-DOS and a LUMO density of states
LUMO-DOS to a predetermine range and disposing them adjacently on
opposites sides of a light emitting layer.
[0038] The effects according to the present invention are not
limited by the contents exemplified above, and more various effects
are included in the present specification.
BRIEF DESCRIPTION OF DRAWINGS
[0039] FIG. 1 is a cross-sectional view illustrating a structure of
an organic EL device according to an embodiment of the present
invention.
MODES FOR CARRYING OUT THE INVENTION
[0040] Advantages and features of the present invention and methods
for achieving them will become apparent with reference to the
embodiments described below in detail in conjunction with the
accompanying drawings. However, the present invention is not
limited to the embodiments disclosed below but may be implemented
in various different forms, the present embodiments are merely
provided to make the disclosure of the present invention complete
and to fully convey the scope of the present invention to those of
ordinary skill in the art, and the present invention is defined
only by the scope of the claims. Thus, in some embodiments,
well-known process steps, well-known device structures and
well-known techniques are not described in detail in order to avoid
obscuring the present invention. Like reference numerals refer to
like elements throughout the specification.
[0041] Unless otherwise defined, all terms used in the present
specification (including technical and scientific terms) may be
used with meanings that may be commonly understood by those skilled
in the art. In addition, the terms defined in the commonly used
dictionaries are not ideally or excessively interpreted, unless
they are specifically defined clearly.
[0042] In addition, throughout the specification, when a part is
said to "include" an element, it means that it may further include
another element, not excluding other elements, unless otherwise
stated. In addition, throughout the specification, "above" or "on"
means not only the case where it is located above or below a target
part but also the case where there is another part in the middle
thereof and does not necessarily mean the upward direction of
gravity. As used herein, the terms "first", "second", and the like
are used to distinguish elements from each other, rather than
indicating any order or importance.
[0043] Throughout this specification, "density of states DOS" may
be defined as the number of allowed states at a particular energy
level, such as HOMO and LUMO, that electrons are allowed to occupy
and a HOMO density of states HOMO-DOS and a LUMO density of states
LUMO-DOS of each material may be obtained in the following
scheme.
[0044] <Organic EL Device>
[0045] Hereinafter, preferred embodiments of the organic EL device
according to the present invention will be described with reference
to the accompanying drawings. However, embodiments of the present
invention may be modified in various other forms, and the scope of
the present invention is not limited to the embodiments described
below.
[0046] FIG. 1 is a cross-sectional view schematically illustrating
a structure of an organic EL device 100 according to an embodiment
of the present invention.
[0047] Referring to FIG. 1, the organic EL device 100 includes an
anode 10; a cathode 20; a light emitting layer 40 between the anode
10 and the cathode 20; a hole transporting area 30 between the
anode 10 and the light emitting layer 40; an electron transporting
area 50 between the light emitting layer 40 and the cathode 20,
where each of the hole transporting area 30 and the electron
transporting area 50 includes at least two layers, an
electron-leakage suppression layer E-LSL 33 is disposed at a
portion of the hole transporting area 30 contacting the light
emitting layer 40, and a hole-leakage suppression layer H-LSL 53 is
disposed at a portion of the electron transporting area 50
contacting the light emitting layer 40.
[0048] That is, when electrons/holes accumulate in the light
emitting layer (e.g., a host), a leakage phenomenon occurs in which
the electrons/holes migrate or diffuse to an adjacent layer,
thereby adversely affecting the efficiency and lifespan
characteristics of the device. Accordingly, in embodiments of the
present invention, an electron-leakage suppression layer and a
hole-leakage suppression layer are disposed on opposite sides of
the light emitting layer as blocking layers that suppress migration
of electrons/holes, and their physical properties are controlled
within a predetermined range to ensure improvement in efficiency
and lifespan of the device.
[0049] Specifically, in the organic EL device according to the
present invention, an electron-leakage suppression layer E-LSL 33
and a hole-leakage suppression layer H-LSL 53 are disposed on
opposite sides of the light emitting layer 40 adjacently thereto,
and an overlap (e.g., overlap ratio) of density of states (DOS) of
HOMO-LUMO values of the electron-leakage suppression layer E-LSL 33
and the hole-leakage suppression layer H-LSL 53 with density of
states (DOS) of HOMO-LUMO values of the host included in the light
emitting layer 40 is controlled to a predetermined range.
Accordingly, the above-described electron/hole leakage phenomenon
may be substantially minimized to increase the efficiency and
lifespan characteristics of the device. In particular, DOS in the
LUMO state may be a more important factor.
[0050] In an embodiment, the density of states of HOMO DOS.sub.HOMO
and the density of states of LUMO DOS.sub.LUMO of the
electron-leakage suppression layer E-LSL and the hole-leakage
suppression layer H-LSL may satisfy at least one of conditions (i)
and (ii) described below.
[0051] In an embodiment, (i) with respect to the density of states
of LUMO, the density of states of LUMO DOS.sub.LUMO.sup.HOST of the
host and the density of states of LUMO DOS.sub.LUMO.sup.H-LSL of
the hole-leakage suppression layer H-LSL 53 overlap each other, and
the density of states of LUMO DOS.sub.LUMO.sup.HOST of the host and
the density of states of LUMO DOS.sub.LUMO.sup.E-LSL of the
electron-leakage suppression layer E-LSL 33 do not overlap each
other.
[0052] That is, electrons move along a LUMO energy level. From the
LUMO-DOS point of view, when the LUMO densities of states of the
hole-leakage suppression layer H-LSL 53 and the host overlap each
other, rapid electron transferring effect may be provided through
the overlap of the LUMO density of states from the hole-leakage
suppression layer H-LSL 53 to the host, thereby achieving
improvement on efficiency of the organic EL device. In addition, in
a case where there is no overlap of the LUMO density of states
between the electron-leakage suppression layer E-LSL 33 and the
host, phenomena that electrons that have migrated to the light
emitting layer are diffused or migrate to, for example, the hole
transporting area 30, for example, the electron-leakage suppression
layer E-LSL 33 may be suppressed, thereby exhibiting an electron
blocking effect. Accordingly, an irreversible decomposition
reaction, caused by oxidation which may occur when electrons
migrate beyond the light emitting layer 40 to the hole transporting
area 30, and a decrease in the lifespan of the organic EL device
arising from the irreversible decomposition reaction may be
prevented, and thus long lifespan characteristics may be
provided.
[0053] In another embodiment, (ii) with respect to the density of
states of HOMO, the density of states of HOMO DOS.sub.HOMO.sup.HOST
of the host and the density of states of HOMO
DOS.sub.HOMO.sup.E-LSL of the electron-leakage suppression layer
E-LSL 33 overlap each other, and the density of states of HOMO
DOS.sub.HOMO.sup.HOST of the host and the density of states of HOMO
DOS.sub.HOMO.sup.H-LSL of the hole-leakage suppression layer H-LSL
53 do not overlap each other.
[0054] Similarly, holes move along a HOMO energy level. From the
HOMO-DOS point of view, when the HOMO densities of states of the
electron-leakage suppression layer E-LSL 33 and the host overlap
each other, rapid hole transferring effect may be provided through
the overlap of the HOMO density of states from the electron-leakage
suppression layer E-LSL 33 to the host, thereby achieving
improvement on efficiency of the organic EL device. In addition, in
a case where there is no overlap of the HOMO density of states
between the hole-leakage suppression layer H-LSL 53 and the host,
phenomena that holes that have migrated to the light emitting layer
are diffused or migrate to, for example, the electron transporting
area 50, for example, the hole-leakage suppression layer H-LSL 53
may be suppressed, thereby exhibiting a hole blocking effect.
[0055] Accordingly, an irreversible decomposition reaction, caused
by oxidation which may occur when electrons migrate beyond the
light emitting layer 40 to the hole transporting area 30, and a
decrease in the lifespan of the organic EL device arising from the
irreversible decomposition reaction may be prevented, and thus long
lifespan characteristics may be provided.
[0056] In another embodiment, the densities of states of LUMO
DOS.sub.LUMO of the electron-leakage suppression layer E-LSL 33 and
the hole-leakage suppression layer H-LSL 53 may satisfy the
aforementioned condition (i), and in addition, the densities of
states of HOMO DOS.sub.HOMO of the electron-leakage suppression
layer E-LSL 33 and the hole-leakage suppression layer H-LSL 53 may
satisfy the aforementioned condition (ii) as well.
[0057] The above-described effects of preventing electron/hole
leakage and improving physical properties of the device such as
efficiency and lifespan arising therefrom may provide synergy
effects as an overlap ratio of the densities of states (e.g., HOMO
DOS, LUMO DOS) between the electron-leakage suppression layer E-LSL
33 and the host; or between the hole-leakage suppression layer
H-LSL 53 and the host increases, because it is more advantageous in
terms of electron/hole mobility. The overlap ratio of the density
of states between the host and the electron-leakage suppression
layer E-LSL 33 or between the host and the hole-leakage suppression
layer H-LSL 53 is not particularly limited and may be appropriately
adjusted in consideration of the above-described physical property
improvement effect.
[0058] In an embodiment, with respect to the density of states of
LUMODOS.sub.LUMO, an overlap ratio between the density of states of
LUMO DOS.sub.LUMO.sup.HOST of the host and the density of states of
LUMO DOS.sub.LUMO.sup.H-LSL of the hole-leakage suppression layer
H-LSL 53 may be more than 0%, specifically more than 0% and 95% or
less, and more specifically 1 to 85%.
[0059] In another embodiment, with respect to the density of states
of HOMO DOS.sub.HOMO, an overlap ratio between the density of
states of HOMO DOS.sub.HOMO.sup.HOST of the host and the density of
states of HOMO DOS.sub.HOMO.sup.E-LSL of the electron-leakage
suppression layer E-LSL 33 may be more than 0%, specifically more
than 0% and 95% or less, and more specifically 1 to 85%.
[0060] In addition, a non-overlap ratio of the density of states
between the host and the electron-leakage suppression layer E-LSL
33 or between the host and the hole-leakage suppression layer H-LSL
53 is not particularly limited and may be appropriately
adjusted.
[0061] In an embodiment, with respect to an absolute value of the
density of states of LUMO DOS.sub.LUMO, a difference between a
minimum LUMO energy value of the density of states of LUMO
DOS.sub.LUMO.sup.HOST of the host and a maximum LUMO energy value
of the density of states of LUMO DOS.sub.LUMO.sup.E-LSL of the
electron-leakage suppression layer E-LSL 33 that do not overlap
each other may be more than 0 eV and 2 eV or less.
[0062] In another embodiment, with respect to an absolute value of
the density of states of HOMO DOS.sub.HOMO, a difference between a
maximum HOMO energy value of the density of states of HOMO
DOS.sub.HOMO.sup.HOST of the host and a minimum HOMO energy value
of the density of states of HOMO DOS.sub.HOMO.sup.H-LSL of the
hole-leakage suppression layer H-LSL 53 that do not overlap each
other may be more than 0 eV and 2 eV or less.
[0063] Each of the electron-leakage suppression layer E-LSL 33 and
the hole-leakage suppression layer H-LSL 53 may have a
single-layered structure of one layer or a multilayered structure
of two or more layers. If the electron-leakage suppression layer
E-LSL 33 and the hole-leakage suppression layer H-LSL 53 have a
multilayered structure of two or more layers, it is preferable that
one electron-leakage suppression layer E-LSL 33 and/or one
hole-leakage suppression layer H-LSL 53 in which density of states
(e.g., HOMO DOS, LUMO DOS) is adjusted is disposed to contact the
light emitting layer 40 directly.
[0064] The electron-leakage suppression layer E-LSL 33 and the
hole-leakage suppression layer H-LSL 53 according to the present
invention may further satisfy at least one of physical properties
described below to achieve a low driving voltage and high
efficiency, in addition to the above-described effects of
preventing leakage of electrons and holes and improving the
mobility of electrons and holes through adjustment of the density
of states DOS.
[0065] In an embodiment, a singlet energy S1.sub.ECL of each of the
electron-leakage suppression layer E-LSL 33 and the hole-leakage
suppression layer H-LSL 53 may be 2.0 eV or more, specifically 2.0
to 4.5 eV, and more specifically 2.0 to 4.0 eV. In such a case,
phenomena that singlet excitons diffuse to an adjacent interface
and/or another layer or that luminescence occurs at an interface
may be suppressed, and the singlet excitons may be effectively
bonded. Accordingly, an amount of excitons is increased, and thus
the luminous efficiency of the organic EL device may be improved.
As a result, it is possible to prevent spectral mixing of the
organic EL device to improve stability, and thus the efficiency and
lifespan of the organic EL device may be improved.
[0066] In another embodiment, a triplet energy T1.sub.ECL of each
of the electron-leakage suppression layer E-LSL 33 and the
hole-leakage suppression layer H-LSL 53 may be 1.5 eV or more,
specifically 1.5 to 4.5 eV, and more specifically 1.5 to 4.0 eV. In
such an embodiment, excitons may be prevented from moving to other
layers, and thus the efficiency of the organic EL device may be
significantly improved.
[0067] In another embodiment, an absolute value of a HOMO (Highest
Occupied Molecular Orbital) of each of the electron-leakage
suppression layer E-LSL 33 and the hole-leakage suppression layer
H-LSL 53 may be 4.5 eV or more, specifically 4.5 to 7.0 eV, and
more specifically 4.5 to 6.5 eV. With this HOMO energy value, it is
possible to block phenomena that holes having transferred to the
light emitting layer 40 diffuse or migrate to another electron
transporting area, for example, the electron transporting layer 52.
Accordingly, it is possible to increase the probability of
recombination that holes and electrons meet each other inside the
light emitting layer 40, thereby further improving the luminous
efficiency of the organic EL device. In addition, the issue of the
irreversible decomposition reaction caused by oxidation which may
occur when electrons migrate beyond the light emitting layer 40 to
the electron transporting layer 52, and the decrease in the
lifespan of the organic EL device arising from the irreversible
decomposition reaction may be solved, and thus the lifespan
characteristics of the device may be improved.
[0068] In another embodiment, an absolute value of a LUMO (Lowest
Unoccupied Molecular Orbital) of each of the electron-leakage
suppression layer E-LSL 33 and the hole-leakage suppression layer
H-LSL 53 may be 1.0 eV or more, specifically 1.0 to 3.5 eV, and
more specifically 1.0 to 3.0 eV. In addition, a band gap energy of
the electron-leakage suppression layer E-LSL 33 and the
hole-leakage suppression layer H-LSL 53 may be 2.5 eV or more, and
specifically 2.5 to 4.5 eV to effectively provide
high-efficiency.
[0069] In another embodiment, a lowest energy level of bond
dissociation energy BDE of each of the electron-leakage suppression
layer E-LSL 33 and the hole-leakage suppression layer H-LSL 53 in a
ground state may be 1.00 eV or more, specifically 1.0 to 6.0 eV,
and more specifically 1.5 to 6.0 eV. In such an embodiment, the
bond dissociation energy BDE may be interpreted as an energy
required to break a specific chemical bond. In general, the bond
dissociation energy BDE is related to stability of molecules as the
bond is stronger, and thus acts as a factor affecting the
lifespan.
[0070] In another embodiment, an absolute value difference
.DELTA.LUMO between the LUMO energy level of the electron-leakage
suppression layer E-LSL 33 and the LUMO energy level of the host
included in the light emitting layer 40 may be 2.0 eV or less, and
specifically, 0 to 2.0 eV.
[0071] In another embodiment, an absolute value difference
.DELTA.HOMO between the HOMO energy level of the electron-leakage
suppression layer E-LSL 33 and the HOMO energy level of the host
included in the light emitting layer 40 may be 2.0 eV or less, and
specifically, 0 to 2.0 eV.
[0072] In another embodiment, an absolute value difference
.DELTA.LUMO between the LUMO energy level of the hole-leakage
suppression layer H-LSL 53 and the LUMO energy level of the host
included in the light emitting layer 40 may be 2.0 eV or less, and
specifically, 0 to 2.0 eV.
[0073] In another embodiment, an absolute value difference
.DELTA.HOMO between the HOMO energy level of the hole-leakage
suppression layer H-LSL 53 and the HOMO energy level of the host
included in the light emitting layer 40 may be 2.0 eV or less, and
specifically, 0 to 2.0 eV.
[0074] For example, the LUMO/HOMO energy level of the hole-leakage
suppression layer H-LSL 53 according to the present invention may
be adjusted so that it is between energy levels of two adjacent
organic layers, for example, the light emitting layer 40 and
another layer in the electron transporting area 50. For example,
the HOMO energy level of the hole-leakage suppression layer H-LSL
53 may be deeper than the HOMO energy level of the light emitting
layer 40 and may be the same as or shallower than the HOMO energy
level of the adjacent another layer 51 or 52 in the electron
transporting area.
[0075] In another example, the LUMO/HOMO energy level of the
electron-leakage suppression layer E-LSL 33 according to the
present invention may be adjusted so that it is between energy
levels of two adjacent organic layers, for example, the light
emitting layer 40 and another layer in the hole transporting area
30. For example, the LUMO energy level of the electron-leakage
suppression layer E-LSL 33 may be deeper than the LUMO energy level
of the light emitting layer 40 and may be the same as or shallower
than the LUMO energy level of the adjacent another layer 31 or 32
in the hole transporting area.
[0076] As described above, when the HOMO/LUMO energy level of the
hole-leakage suppression layer H-LSL 53 and/or electron-leakage
suppression layer E-LSL 33 is satisfied, HOMO/LUMO energy levels of
the organic layers disposed with respect to the light emitting
layer 40 adjacently thereto, e.g., the hole transporting area 30
and the electron transporting area 50 may be arranged in a step
manner. Accordingly, holes transferred through the anode 10 and
electrons transferred through the cathode 20 may be transferred
more smoothly to the light emitting layer 40 through the stepwise
arrangement of the organic layer A, and thus it is possible to
increase the formation of excitons and improve efficiency of the
device.
[0077] In another embodiment, an electron affinity EA of the
hole-leakage suppression layer H-LSL 53 may be at least 0.5 eV or
more, and specifically 0.5 to 3.0 eV. In the case where the
hole-leakage suppression layer H-LSL 53 has the aforementioned
electron affinity, high electron injection efficiency may be
obtained.
[0078] In another embodiment, in a case where the light emitting
layer 40 is a blue light emitting layer containing a blue
fluorescent light emitting material, each of the electron-leakage
suppression layer E-LSL 33 and the hole-leakage suppression layer
H-LSL 53 may have a refractive index n of at least 0.6 or more, and
specifically 0.6 to 3.5, in a blue wavelength range of 400 to 470
nm.
[0079] If electrons and holes are not balanced due to a difference
between the number of holes injected from the anode 10 and the
number of electrons injected from the cathode 20, the electrons or
holes that fail to form excitons by recombination may be
accumulated in the light emitting layer 40. The electrons or holes
accumulated in the light emitting layer 40 interfere with smooth
oxidation and reduction from occurring in the light emitting layer
40, or affect adjacent layers, and thus the lifespan of the organic
EL device may be reduced. On the other hand, each of the
electron-leakage suppression layer E-LSL 33 and the hole-leakage
suppression layer H-LSL 53 has an electron mobility (p) of at least
1.times.10.sup.-8 cm.sup.2/Vs or more at room temperature, such
that the delay of the injection of electrons as compared to the
number of holes injected from the anode 10 is prevented, and the
injection of electrons into the light emitting layer 40 becomes
smooth. Accordingly, efficiency of exciton formation in the light
emitting layer 40 is increased, and thus the lifespan of the
organic EL device may be improved.
[0080] Hereinafter, the configuration of the organic EL device 100
including the above-described electron-leakage suppression layer
E-LSL 33 and/or hole-leakage suppression layer H-LSL 53 according
to an embodiment of the present invention will be described in more
detail.
[0081] Anode
[0082] In the organic EL device 100 according to the present
invention, the anode 10 serves to inject holes into an organic
layer A.
[0083] A material forming the anode 10 is not particularly limited,
and conventional materials known in the art may be used.
Non-limiting examples thereof may include metals such as vanadium,
chromium, copper, zinc and gold; alloys thereof; metal oxides such
as zinc oxide, indium oxide, indium tin oxide (ITO) and indium zinc
oxide (IZO); a combination of a metal and an oxide such as ZnO:Al
and SnO.sub.2:Sb; conductive polymers such as polythiophene,
poly(3-methylthiophene),
poly[3,4-(ethylene-1,2-dioxy)thiophene](PEDT), polypyrrole and
polyaniline, and carbon black.
[0084] A method of manufacturing the anode 10 is also not
particularly limited and it may be prepared according to
conventional methods known in the art. As an example, a method of
coating an anode material on a substrate formed of a silicon wafer,
quartz, a glass plate, a metal plate or a plastic film may be
used.
[0085] Cathode
[0086] In the organic EL device 100 according to the present
invention, the cathode 20 serves to inject electrons into the
organic layer A.
[0087] A material forming the cathode 20 is not particularly
limited, and conventional materials known in the art may be used.
Non-limiting examples thereof may include metals such as magnesium,
calcium, sodium, potassium, titanium, indium, yttrium, lithium,
gadolinium, aluminum, silver, tin, and lead, alloys thereof, and
multilayer-structured materials such as LiF/Al and
LiO.sub.2/Al.
[0088] In addition, a method of manufacturing the cathode 20 is not
also particularly limited and it may be prepared according to
conventional methods known in the art.
[0089] Organic Layer
[0090] The organic layer A included in the organic EL device
according to the present invention may use, without limitation, any
conventional configuration used in an organic layer of conventional
organic EL devices, and may include, for example, one or more
selected from the hole transporting area 30, the light emitting
layer 40, and the electron transporting area 50. In such a case, in
consideration of the characteristics of the organic EL device, it
is preferable to include all the above-mentioned organic
layers.
[0091] Hole Transporting Area
[0092] The hole transporting area 30 included in the organic layer
A of the present invention serves to transfer holes injected from
the anode 10 to the light emitting layer 40.
[0093] The hole transporting area 30 may include two or more layers
including at least one of the electron-leakage suppression layer
E-LSL 33, the hole injection layer 31 and the hole transporting
layer 32 described above.
[0094] The hole transporting area 30 may have a structure in which
the electron-leakage suppression layer E-LSL 33 and the hole
injection layer 31 are disposed with respect to the light emitting
layer; or a structure in which the electron-leakage suppression
layer E-LSL 33, the hole transporting layer 32, and the hole
injection layer 31 are disposed with respect to the light emitting
layer. Considering the characteristics of the organic EL device, it
is preferable to include all of the electron-leakage suppression
layer E-LSL 33, the hole injection layer 31 and the hole
transporting layer 32.
[0095] The electron-leakage suppression layer E-LSL 33 according to
the present invention is not particularly limited in terms of
detailed configuration of a compound forming the electron-leakage
suppression layer E-LSL 33, such as the type of moiety contained in
the compound (e.g., EDG group, EWG group) and its binding position,
introduction position of a linker, and its composition, as long as
it satisfies the above-described density of states (e.g., HOMO DOS,
LUMO DOS) overlap parameters and corresponding values.
[0096] In an embodiment, a compound that may be used as a material
for the electron-leakage suppression layer E-LSL 33 may be
represented by the following Formula 1.
##STR00001##
[0097] In Formula 1,
[0098] L.sub.1 to L.sub.3 may be the same as or different from each
other, each independently being a single bond or selected from the
group consisting of a C.sub.4 to C.sub.60 arylene group and a
C.sub.4 to C.sub.60 heteroarylene group,
[0099] Ar.sub.1 to Ar.sub.3 may be the same as or different from
each other, each independently being selected from the group
consisting of hydrogen, deuterium, a halogen group, a cyano group,
a nitro group, an amino group, a C.sub.1 to C.sub.40 alkyl group, a
C.sub.2 to C.sub.40 alkenyl group, a C.sub.2 to C.sub.40 alkynyl
group, a C.sub.3 to C.sub.40 cycloalkyl group, a heterocycloalkyl
group having 3 to 40 nuclear atoms, a C.sub.6 to C.sub.60 aryl
group, a heteroaryl group having 5 to 60 nuclear atoms, a C.sub.1
to C.sub.40 alkyloxy group, a C.sub.6 to C.sub.60 aryloxy group, a
C.sub.1 to C.sub.40 alkylsilyl group, a C.sub.6 to C.sub.60
arylsilyl group, a C.sub.1 to C.sub.40 alkylboron group, a C.sub.6
to C.sub.60 arylboron group, a C.sub.6 to C.sub.60 arylphosphine
group, a C.sub.6 to C.sub.60 arylphosphine oxide group, and a
C.sub.6 to C.sub.60 arylamine group,
[0100] the arylene group and the heteroarylene group of L.sub.1 to
L.sub.3; and the alkyl group, the alkenyl group, the alkynyl group,
the aryl group, the heteroaryl group, the aryloxy group, the
alkyloxy group, the cycloalkyl group, the heterocycloalkyl group,
the arylsilyl group, the alkylsilyl group, the alkylboron group,
the arylboron group, the arylphosphine group, the arylphosphine
oxide group and the arylamine group of Ar.sub.1 to Ar.sub.3 may
each independently be substituted with one or more kinds of
substituents selected from the group consisting of hydrogen,
deuterium, halogen, a cyano group, a nitro group, a C.sub.1 to
C.sub.40 alkyl group, a C.sub.2 to C.sub.40 alkenyl group, a
C.sub.2 to C.sub.40 alkynyl group, a C.sub.3 to C.sub.40 cycloalkyl
group, a heterocycloalkyl group having 3 to 40 nuclear atoms, a
C.sub.6 to C.sub.60 aryl group, a heteroaryl group having 5 to 60
nuclear atoms, a C.sub.1 to C.sub.40 alkyloxy group, a C.sub.6 to
C.sub.60 aryloxy group, a C.sub.1 to C.sub.40 alkylsilyl group, a
C.sub.6 to C.sub.60 arylsilyl group, a C.sub.1 to C.sub.40
alkylboron group, a C.sub.6 to C.sub.60 arylboron group, a C.sub.6
to C.sub.60 arylphosphine group, a C.sub.6 to C.sub.60
arylphosphine oxide group and a C.sub.6 to C.sub.60 arylamine
group, and when the substituents are plural in number, the
substituents are the same as or different from each other.
[0101] The compound that may be used as a material for the
electron-leakage suppression layer E-LSL 33 of the present
invention described above may be further embodied as exemplary
compounds to be described below. However, the compound constituting
the electron-leakage suppression layer E-LSL 33 according to the
present invention is not limited by those illustrated below.
Particularly, if physical properties such as an overlap of density
of states (e.g., HOMO DOS, LUMO DOS) are satisfied, the type of
moiety (e.g., EDG group, EWG group) included in the compound and
its binding position, and an introduction position of a linker are
not particularly limited. In addition, compounds having various
modifications in their chemical structures belong to the scope of
the present invention.
[0102] The electron-leakage suppression layer E-LSL 33 according to
the present invention may be manufactured through conventional
methods known in the art. Examples thereof may include, but not
limited to, a vacuum deposition method, spin coating method, cast
method, LB (Langmuir-Blodgett), inkjet printing method, laser
printing method, LITI (Laser Induced Thermal Imaging) and the
like.
[0103] In the hole transporting area 30 according to the present
invention, materials for the hole injection layer 31 and/or the
hole transporting layer 32, used together with the electron-leakage
suppression layer E-LSL 33, are not particularly limited, and any
hole injection/transporting layer material known in the art may be
used without limitation, as long as it has a low hole injection
barrier and a high hole mobility. In such a case, the materials
forming the hole injection layer 31 and the hole transporting layer
32 may be the same as or different from each other.
[0104] The hole injection material may use, without limitation, any
hole injection material known in the art. Non-limiting examples of
the hole injection material may include phthalocyanine compounds
such as copper phthalocyanine; DNTPD
(N,N'-diphenyl-N,N'-bis-[4-(phenyl-m-tolyl-amino)-phenyl]-biphenyl-4,4'-d-
iamine), m-MTDATA (4,4',4''-tris
(3-methylphenylphenylamino)triphenylamine), TDATA
(4,4'4''-Tris(N,N-diphenylamino)triphenylamine), 2TNATA
(4,4',4''-tris{N-(2-naphthyl)-N-phenylamino}-triphenylamine),
PEDOT/PSS
(poly(3,4-ethylenedioxythiophene)/poly(4-styrenesulfonate)),
PANI/DBSA (polyaniline/dodecylbenzenesulfonic acid), PANI/CSA
(polyaniline/camphor sulfonic acid), PANI/PSS
(polyaniline)/poly(4-styrenesulfonate)), and the like, which may be
used solely or as a mixture of two or more thereof.
[0105] The hole transporting material may use, without limitation,
any hole transporting material known in the art. Non-limiting
examples of the hole transporting material may include
carbazole-based derivatives such as phenylcarbazole,
polyvinylcarbazole or the like; fluorine-based derivatives;
triphenylamine-based derivatives such as TPD
(N,N'-bis(3-methylphenyl)-N,N'-diphenyl-[1,1-biphenyl]-4,4'-diamine),
TCTA (4,4',4''-tris(N-carbazolyl)triphenylamine) or the like; NPB
(N,N'-di(1-naphthyl)-N,N'-diphenylbenzidine),
TAPC(4,4'-cyclohexylidene bis[N,N-bis(4-methylphenyl)benzenamine]),
and the like, which may be used solely or as a mixture of two or
more thereof.
[0106] The hole transporting area 30 may be formed through any
conventional method known in the art. Examples of the method may
include, but are not limited to, a vacuum deposition method, a spin
coating method, a cast method, a Langmuir-Blodgett (LB) method, an
inkjet printing method, a laser printing method, a laser-induced
thermal imaging (LITI) method, and the like.
[0107] Light Emitting Layer
[0108] The light emitting layer 40 included in the organic layer A
of the present invention is a layer in which holes and electrons
meet each other forming excitons, and a color of light emitted by
the organic EL device may vary according to the material forming
the light emitting layer 40.
[0109] Such a light emitting layer 40 may include a host and a
dopant, and a mixing ratio thereof may be appropriately adjusted
within a range known in the art. For example, the light emitting
layer 40 may include the host in an amount ranging from 70 to 99.9
percent by weight (hereinafter, "wt %") and the dopant in an amount
ranging from 0.1 to 30 wt %, with respect to the total weight of
the light emitting layer 40. More specifically, when the light
emitting layer 40 is blue fluorescence, green fluorescence, or red
fluorescence, the host may be included in an amount ranging from 80
to 99.9 wt %, and the dopant may be included in an amount ranging
from 0.1 to 20 wt %. In addition, when the light emitting layer 40
is blue fluorescence, green fluorescence or red phosphorescence,
the host may be included in an amount ranging from 70 to 99 wt %
and the dopant may be included in an amount ranging from 1 to 30 wt
%.
[0110] Any host known in the art may be included in the light
emitting layer 40 of the present invention without particular
limitation, and non-limiting examples thereof may include alkali
metal complex compounds, alkaline earth metal complex compounds, or
fused aromatic cyclic derivatives.
[0111] More specifically, the host material is preferably aluminum
complex compounds, beryllium complex compounds, anthracene
derivatives, pyrene derivatives, triphenylene derivatives,
carbazole derivatives, dibenzofuran derivatives, dibenzothiophene
derivatives, or a combination of one or more kinds thereof that may
enhance luminous efficiency and lifespan of the organic EL
device.
[0112] In addition, any dopant known in the art may be included in
the light emitting layer 40 of the present invention without
particular limitation, and non-limiting examples thereof may
include anthracene derivatives, pyrene derivatives, arylamine
derivatives, and metal complex compounds including iridium (Ir) or
platinum (Pt).
[0113] Such dopants may be classified into red dopants, green
dopants, and blue dopants, and any conventional red dopants, green
dopants, and blue dopants that are known in the art may be used
without particular limitation.
[0114] More specifically, non-limiting examples of the red dopant
may include PtOEP (Pt(II) octaethylporphyrin), Ir(piq).sub.3
(tris(2-phenylisoquinoline) iridium), Btp.sub.2Ir (acac) (bis
(2-(2'-benzothienyl)-pyridinato-N,C3') iridium(acetylacetonate)),
or a mixture of two or more thereof.
[0115] Furthermore, non-limiting examples of the green dopant may
include Ir(ppy).sub.3 (tris(2-phenylpyridine) iridium),
Ir(ppy).sub.2(acac) (bis(2-phenylpyridine) (acetylacetonato)
iridium(III)), Ir(mppy).sub.3 (tris(2-(4-tolyl)phenylpiridine)
iridium), C545T
(10-(2-benzothiazolyl)-1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H,11H-[-
1]benzopyrano[6,7,8-ij]-quinolizin-11-one), or a mixture of two or
more thereof.
[0116] Furthermore, non-limiting examples of the blue dopant may
include F.sub.2Irpic (bis[3,5-difluoro-2-(2-pyridyl)phenyl]
(picolinato) iridium(III)), (F.sub.2ppy).sub.2Ir(tmd),
Ir(dfppz).sub.3, DPVBi (4,4'-bis(2,2'-diphenylethen-1-yl)biphenyl),
DPAVBi (4,4'-bis[4-(diphenylamino) styryl]biphenyl), TBPe
(2,5,8,11-tetra-tert-butylperylene), or a mixture of two or more
thereof.
[0117] The light emitting layer 40 according to the present
invention may be a red light emitting layer including a red
phosphorescent material, a green light emitting layer including a
green phosphorescent material; or a blue light emitting layer
including a blue phosphorescent material or a blue fluorescent
material. The light emitting layer 40 may preferably be a light
emitting layer including a blue fluorescent material.
[0118] The light emitting layer 40 may include a single layer
including one type of material, a single layer including a
plurality of different materials, or a multi-layer of at least two
layers, each including different materials from each other. When
the light emitting layer 40 includes a plurality of layers, the
organic EL device may emit light having various colors.
Specifically, the present invention may provide an organic EL
device having mixed colors by including a plurality of light
emitting layers, including different kinds of materials, in series.
In addition, when the light emitting layer 40 includes a plurality
of light emitting layers, the driving voltage of the device may
increase, while the current value in the organic EL device become
constant, and thus the organic EL device may have luminous
efficiency that is improved by the number of the light emitting
layers.
[0119] Although not illustrated in the drawings, the organic EL
device 100 may include a plurality of light emission stacks (not
illustrated) including at least one light emitting layer.
[0120] The plurality of light emitting layers included in the light
emission stack may be light emitting layers that emit light of
different colors, or light emitting layers that emit light of the
same color. That is, the emission color may vary depending on the
material forming the light emitting layer. For example, the
plurality of light emission stacks may include a material emitting
blue, green, red, yellow, white, or the like, and may be formed
using phosphorescent or fluorescent materials. In this case, the
colors represented by the light emitting layers may be
complementary to each other. In addition, a color may be selected
as a combination of colors capable of emitting white light. Each of
the light emitting layers may include phosphorescent dopants or
fluorescent dopants corresponding to the selected color,
respectively.
[0121] Although not illustrated in the drawings, the organic EL
device 100 may further include a charge generation layer CGL (not
illustrated) disposed between adjacent stacks of the plurality of
light emission stacks and connecting them.
[0122] The charge generation layer CGL means a layer, in the
organic EL device including a plurality of light emission stacks,
that separates light emission stacks adjacent to each other without
directly contacting both electrodes (e.g., anode and cathode). Such
a charge generation layer CGL is disposed between two adjacent
light emission stacks, generating electrons to serve as a cathode
for one light emission stack, and generating holes to serve as an
anode for another light emission stack. The charge generation layer
CGL may use, without limitation, any material that may be used as a
charge generation layer material known in the art. In addition, a
conventional n-type and/or p-type material known in the art may be
doped to the above material for the charge generation layer.
[0123] Electron Transporting Area
[0124] In the organic EL device 100 according to the present
invention, the electron transporting area 50 included in the
organic layer A serves to transfer electrons injected from the
cathode 20 to the light emitting layer 40.
[0125] The electron transporting area 50 may include two or more
layers including the hole-leakage suppression layer H-LSL 53; and
at least one of the electron transporting layer 52 and the electron
injection layer 51, and may further include an electron
transporting auxiliary layer (not illustrated) if necessary.
[0126] The electron transporting area 50 may have a structure in
which the hole-leakage suppression layer H-LSL 53 and the electron
injection layer 51 are disposed with respect to the light emitting
layer or a structure in which the hole-leakage suppression layer
H-LSL 53, the electron transporting layer 52, and the electron
injection layer 51 are disposed with respect to the light emitting
layer. Considering characteristics of the organic EL device, it is
preferable to include all of the hole-leakage suppression layer
H-LSL 53, the electron injection layer 51 and the electron
transporting layer 52.
[0127] The hole-leakage suppression layer H-LSL 53 according to the
present invention is not particularly limited in terms of detailed
configuration of a compound forming the hole-leakage suppression
layer H-LSL 53, such as the type of moiety contained in the
compound (e.g., EDG group, EWG group) and its binding position,
introduction position of a linker, and its composition, as long as
it satisfies the above-described density of states (e.g., HOMO DOS,
LUMO DOS) overlap parameters and corresponding values.
[0128] In an embodiment, the compound included as a material for
the hole-leakage suppression layer H-LSL 53 may be a compound
bonded with at least one moiety, known in the art, having EWG
characteristics with high electron absorptivity, and may be, for
example, a bipolar compound including both of a moiety having EWG
characteristics with high electron absorptivity and a moiety having
EDG characteristics with high electron donating properties.
[0129] More specifically, the compound (material) forming the
hole-leakage suppression layer H-LSL 53 may include at least one
EWG moiety including at least one of a 6-membered moiety
represented by the following Formula 2; a 5-membered moiety
represented by the following Formula 3; and a polycyclic moiety in
which the 6-membered moiety and the 5-membered moiety are
fused.
##STR00002##
[0130] In Formula 2 or 3,
[0131] X.sub.1 to X.sub.6 and Y.sub.1 to Y.sub.5 may be the same as
or different from each other, each independently being N or C(R),
while at least one of X.sub.1 to X.sub.6 and Y.sub.1 to Y.sub.5 is
N,
[0132] when C(R) is plural in number, the plurality of R may be the
same as or different from each other, each independently being
selected from the group consisting of: hydrogen, deuterium, a
halogen group, a cyano group, a nitro group, an amino group, a
C.sub.1 to C.sub.40 alkyl group, a C.sub.2 to C.sub.40 alkenyl
group, a C.sub.2 to C.sub.40 alkynyl group, a C.sub.3 to C.sub.40
cycloalkyl group, a heterocycloalkyl group having 3 to 40 nuclear
atoms, a C.sub.6 to C.sub.60 aryl group, a heteroaryl group having
5 to 60 nuclear atoms, a C.sub.1 to C.sub.40 alkyloxy group, a
C.sub.6 to C.sub.60 aryloxy group, a C.sub.1 to C.sub.40 alkylsilyl
group, a C.sub.6 to C.sub.60 arylsilyl group, a C.sub.1 to C.sub.40
alkylboron group, a C.sub.6 to C.sub.60 arylboron group, a C.sub.6
to C.sub.60 arylphosphine group, a C.sub.6 to C.sub.60
arylphosphine oxide group and a C.sub.6 to C.sub.60 arylamine
group, or may be bonded with an adjacent group to form a fused
ring,
[0133] the alkyl group, the alkenyl group, the alkynyl group, the
aryl group, the heteroaryl group, the aryloxy group, the alkyloxy
group, the cycloalkyl group, the heterocycloalkyl group, the
arylamine group, the alkylsilyl group, the alkylboron group, the
arylboron group, the arylphosphine group, the arylphosphine oxide
group, and the arylamine group of R may each independently be
substituted with one or more kinds of substituents selected from
the group consisting of hydrogen, deuterium (D), halogen, a cyano
group, a nitro group, a C.sub.1 to C.sub.40 alkyl group, a C.sub.2
to C.sub.40 alkenyl group, a C.sub.2 to C.sub.40 alkynyl group, a
C.sub.3 to C.sub.40 cycloalkyl group, a heterocycloalkyl group
having 3 to 40 nuclear atoms, a C.sub.6 to C.sub.60 aryl group, a
heteroaryl group having 5 to 60 nuclear atoms, a C.sub.1 to
C.sub.40 alkyloxy group, a C.sub.6 to C.sub.60 aryloxy group, a
C.sub.1 to C.sub.40 alkylsilyl group, a C.sub.6 to C.sub.60
arylsilyl group, a C.sub.1 to C.sub.40 alkylboron group, a C.sub.6
to C.sub.60 arylboron group, a C.sub.6 to C.sub.60 arylphosphine
group, a C.sub.6 to C.sub.60 arylphosphine oxide group and a
C.sub.6 to C.sub.60 arylamine group, and when the substituents are
plural in number, the substituents may be the same as or different
from each other.
[0134] The compound (material) forming the hole-leakage suppression
layer H-LSL 53 exhibits excellent electronic properties by
including at least one nitrogen (N)-containing heteroaromatic ring
containing nitrogen (N), that is, an EWG (electron withdrawing
group). Accordingly, when the compound having the 6-membered or
5-membered moiety represented by Chemical Formula 2 or 3, or having
a polycyclic moiety in which they are fused is used as a material
for the hole-leakage suppression layer H-LSL 53, the hole-leakage
suppression layer H-LSL 53 may well receive electrons from the
cathode 20 to transfer the electrons to the light emitting layer 40
smoothly, and accordingly, the driving voltage of the device 100
may be reduced and high efficiency and long life of the device 100
may be resulted.
[0135] In addition, the material of the hole-leakage suppression
layer H-LSL 53 not only has a high triplet energy, but also has a
molecular weight of the compound significantly increased through
the control of various types of substituents introduced into a
mother nucleus and location of the introduction, and thus an
improved glass transition degree and high thermal stability may be
achieved. In addition, since it is also effective in suppressing
crystallization of the organic layer, the organic EL device 100
including the hole-leakage suppression layer H-LSL 53 may greatly
improve durability and lifespan characteristics.
[0136] According to an embodiment of the present invention, the EWG
moiety included in the compound forming the hole-leakage
suppression layer H-LSL 53 may be embodied as, but not limited to,
any one selected from the following structural group.
##STR00003##
[0137] In the above formulas,
[0138] * means a site where a bond is made with a compound that
forms a hole-leakage suppression layer.
[0139] Although not specifically indicated in the above structural
formulas, at least one or more substituents (e.g., the same as the
definition of R) known in the art may be substituted. In addition,
although one site * connected to the compound forming the
hole-leakage suppression layer H-LSL 53 is shown in the structural
formula, it will be understood that a case where two sites are
included is within the scope of the present invention.
[0140] In an embodiment according to the present invention, the
compound forming the hole-leakage suppression layer H-LSL 53 may
include at least one conventional EDG moiety known in the pertinent
art, other than the aforementioned EWG, that has higher electron
donating properties than that of the EWG.
[0141] The compound that may be used as the material forming the
hole-leakage suppression layer H-LSL 53 of the present invention
may be further embodied as exemplary compounds described below.
However, the compound forming the hole-leakage suppression layer
H-LSL 53 according to the present invention is not limited by those
illustrated below. In particular, as long as the physical
properties such as DOS overlap ratio are satisfied, the type of
moieties (e.g., EDG group and EWG group) included in the compound,
its binding site, and the linking position of the linker are not
particularly limited, and the compound with various modified
structures are also within the scope of the present invention.
[0142] The hole-leakage suppression layer H-LSL 53 according to the
present invention may be formed using any conventional method known
in the art without particular limitation, for example, a vacuum
deposition method, a spin coating method, a cast method, a
Langmuir-Blodgett (LB) method, an inkjet printing method, a laser
printing method, a laser-induced thermal imaging (LITI) method, and
the like.
[0143] In the electron transporting area 50 according to the
present invention, materials for the electron transporting layer 52
and the electron injection layer 51, used together with the
hole-leakage suppression layer H-LSL 53, are not particularly
limited, and any electron injection/transporting layer material
known in the art may be used without limitation, as long as it
facilitates electron injection and has a high electron mobility. In
such a case, the materials forming the electron transporting layer
52 and the electron injection layer 51 may be the same as or
different from each other.
[0144] Non-limiting examples of electron injection materials that
may be used include anthracene derivatives, heteroaromatic
compounds, alkali metal complexes, and the like. Specifically,
examples thereof may include lanthanum group metals such as LiF,
Li.sub.2O, BaO, NaCl, CsF, Yb and the like; or a metal halide such
as RbCl, RbI, or the like, which may be used solely or in
combination of two or more thereof.
[0145] In addition, the electron transporting layer 52 may use a
material having conventional electron transporting characteristics
known in the art without limitation. For example, oxadiazole
derivatives, triazole derivatives, phenanthroline derivatives
(e.g., BCP), heterocyclic derivatives including nitrogen, and the
like may be included.
[0146] The electron transporting area 50 according to the present
invention, specifically, the electron injection layer 52 and the
electron transporting layer 52 may use a material co-deposited with
an n-type dopant so that electrons may be easily injected from the
cathode. In such a case, an alkali metal complex known in the art
may be used as the n-type dopant without limitation, and examples
thereof may include an alkali metal, an alkaline earth metal, or a
rare earth metal.
[0147] The electron transporting area 50 may be manufactured
through conventional methods known in the art. Examples thereof may
include a vacuum deposition method, spin coating method, cast
method, LB (Langmuir-Blodgett), inkjet printing method, laser
printing method, LITI (Laser Induced Thermal Imaging) and the like,
but are not limited thereto.
[0148] Auxiliary Light Emitting Layer
[0149] Optionally, the organic EL device 100 according to the
present invention may further include an auxiliary light emitting
layer (not illustrated) disposed between the hole transporting area
30 and the light emitting layer 40.
[0150] The auxiliary light emitting layer serves to transfer holes
migrating from the hole transporting area 30 to the light emitting
layer 40 and to control a thickness of the organic layer A. The
auxiliary light emitting layer has a high LUMO value to prevent
electrons from moving to the hole transporting layer 32 and has a
high triplet energy to prevent the excitons of the light emitting
layer 40 from diffusing into the hole transporting layer 32.
[0151] The auxiliary light emitting layer may include a hole
transporting material and may include a material the same as a
material for the hole transporting area. In addition, the auxiliary
light emitting layers of the red, green, and blue organic EL
devices may be formed of the same material.
[0152] The material of the auxiliary light emitting layer is not
particularly limited, and examples thereof may include carbazole
derivatives and arylamine derivatives. Non-limiting examples of the
auxiliary light emitting layer that are applicable may include NPD
(N, N-dinaphthyl-N, N'-diphenyl benzidine), TPD (N,
N'-bis-(3-methylphenyl)-N, N'-bis(phenyl)-benzidine), s-TAD, and
MTDATA(4,4',4-Tris(N-3-methylphenyl-Nphenyl-amino)-triphenylamine).
They may be used solely or in combination of two or more thereof.
In addition, the auxiliary light emitting layer may include a
p-type dopant, in addition to the above materials. As the p-type
dopant, any well-known p-type dopant used in the art may be
used.
[0153] Capping Layer
[0154] Optionally, the organic EL device 100 of the present
invention may further include a capping layer (not illustrated)
disposed on the cathode 20 described above. The capping layer
serves to protect the organic EL device and to help light emitted
from the organic layer to be efficiently emitted to the
outside.
[0155] The capping layer may include at least one selected from the
group consisting of tris-8-hydroxyquinoline aluminum (Alq.sub.3),
ZnSe,
2,5-bis(6'-(2',2''-bipyridyl))-1,1-dimethyl-3,4-diphenylsilole,
4'-bis [N-(1-napthyl)-N-phenyl-amion] biphenyl (.alpha.-NPD),
N,N'-diphenyl-N,N'-bis (3-methylphenyl)-1,1'-biphenyl-4,4'-diamine
(TPD), and 1,1'-bis(di-4-tolylaminophenyl) cyclohexane (TAPC). A
material forming such a capping layer is less expensive than
materials of other layers of the organic EL device.
[0156] The capping layer may be a single layer, or may include two
or more layers having different refractive indices so that the
refractive index gradually changes along the two or more
layers.
[0157] The capping layer may be manufactured by a conventional
method known in the art, and for example, various methods such as
vacuum deposition, spin coating, casting, or Langmuir-Blodgett (LB)
method may be used.
[0158] The organic EL device of the present invention including the
above-described configuration may be manufactured according to
conventional methods known in the art. For example, the organic EL
device may be manufactured by vacuum depositing an anode material
on a substrate and then vacuum depositing a material of the hole
transporting area, a material of the light emitting layer, a
material of the electron transporting area, and a material of the
cathode on the anode in the order.
[0159] Meanwhile, a structure in which the hole transporting area
30 and the electron transporting area 50 are disposed on opposite
sides of the light emitting layer 40, where the electron-leakage
suppression layer E-LSL 33, the hole transporting layer 32 and the
hole injection layer 31 are disposed at the hole transporting area
30 and the hole-leakage suppression layer H-LSL 53, the electron
transporting layer 52 and the electron injection layer 51 are
disposed at the electron transporting area 50 is described in FIG.
1 by way of example. However, the present invention is not limited
to the above-described configuration, and various modifications are
possible. For example, a structure in which the hole transporting
area 30 includes the electron-leakage suppression layer E-LSL 33
and one layer 31 or 32, a structure in which the electron
transporting area 50 includes the hole leakage suppression layer
H-LSL 53 and one layer 51 or 52, or a structure in which the hole
transporting area 30 includes the electron-leakage suppression
layer E-LSL 33 and one layer 31 or 32 and the electron transporting
area 50 includes the hole leakage suppression layer H-LSL 53 and
one layer 51 or 52 is also within the scope of the present
invention.
[0160] The organic EL device 100 according to the present invention
has a structure in which the anode 10, the organic layer A, and the
cathode 20 are sequentially stacked, and an insulating layer or an
adhesive layer may be further included between the anode 10 and the
organic layer A or between the cathode 20 and the organic layer A.
Such an organic EL device of the present invention may have
excellent lifespan characteristics since the lifetime (e.g.,
half-time) of the initial brightness is increased while maintaining
the maximum luminous efficiency when voltage, current, or both are
applied.
[0161] Hereinafter, the present invention will be described in
detail with reference to embodiments, but the following embodiments
are merely illustrative of the present invention, and the present
invention is not limited by the following embodiments.
PREPARATION EXAMPLE
[0162] The compounds according to the present invention were
prepared as follows, and their physical properties were measured by
methods known in the art, respectively, which are shown in Table 1
below.
[0163] The HOMO energy, the LUMO energy, the singlet energy S1, the
triplet energy T1 and the like of the material used in the present
invention were calculated using a Schrodinger program (Schrodinger
software release 2020-1). Specifically, the basic calculation
scheme of each property used the B3LYP functional (Becke,
3-parameter, Lee-Yang-Parr) which is most widely used among density
functional theories (DFT), and triple zeta (TZV) was used as a
basis set to optimize the molecular structure.
[0164] The HOMO energy and the LUMO energy of each compound were
calculated in the ground state S0 with the optimized structure, and
each of the singlet energy S1 and the triplet energy T1 was
calculated based on the optimized energy difference between the
ground state S0/singlet energy S1 and ground state S0/triplet
energy T1.
[0165] In addition, the DOS (density of states) was obtained using
molecular dynamics and quantum mechanics. For example, firstly, a
simulation of hundreds to thousands of atoms was conducted through
molecular dynamics, the HOMO and LUMO energies of all the molecules
were then obtained using the quantum mechanics, and the DOS was
then obtained based on them. The materials for the electron-leakage
suppression layer E-LSL and the hole-leakage suppression layer
H-LSL were compared with the host materials mixed together, and a
DOS overlap ratio was percentaged.
[0166] In addition, a bond dissociation energy (BDE), a refractive
index, and a dipole moment were obtained using the aforementioned
B3LYP/TZV method, and in particular, for the BDE, an energy
required to break a certain chemical bond in a molecule is
calculated, and a value having a smallest BDE was selected.
TABLE-US-00001 TABLE 1 Host overlap S1 T1 Refractive Dipole HOMO
LUMO ratio (%) energy energy index BDE moment Color Compound (eV)
(eV) HOMO LUMO (eV) (eV) (450 nm) (eV) (Debye) Blue 1 H-LSL-1 -6.09
-2.1 0 45 3.65 2.62 1.85 2.43 2.52 E-LSL-1 -5.23 -1.37 38 0 3.23
2.47 1.72 1.53 0.13 2 H-LSL-2 -6.39 -2.29 0 0 3.68 2.68 2.12 1.22
2.08 E-LSL-2 -5.26 -1.5 47 0 3.02 2.43 1.12 2.03 1.16 3 H-LSL-3
-6.05 -1.99 0 71 3.68 2.6 1.22 2.66 7.89 E-LSL-3 -5.33 -1.73 62 0
3.04 2.3 1.62 1.74 0.82 4 H-LSL-4 -5.81 -2.05 0 67 3.43 2.33 1.81
3.01 3.38 E-LSL-4 -5.11 -1.69 0 0 3.03 2.39 1.88 2.54 1.67 5
H-LSL-5 -6.26 -2.29 0 28 3.27 2.70 2.07 1.98 3.04 E-LSL-5 -5.31
-1.78 58 0 3.03 2.4 0.98 1.71 1.28 Green 6 H-LSL-6 -6.11 -2.51 0 74
3.14 2.43 1.58 3.25 5.73 E-LSL-6 -5.32 -1.42 53 0 3.39 2.6 1.71
2.25 1.85 7 H-LSL-7 -6.04 -2.15 0 0 3.8 2.43 1.97 3.02 6.97 E-LSL-7
-5.27 -1.33 23 0 3.34 2.51 2.11 2.07 1.69 8 H-LSL-8 -6.23 -2.52 0
62 3.68 2.98 1.89 2.33 0.25 E-LSL-8 -5.31 -1.71 45 0 3.22 2.50 1.93
2.16 0.68 9 H-LSL-9 -6.3 -2.47 0 63 3.66 2.60 2.23 3.41 7.15
E-LSL-9 -5.12 -1.62 0 0 3.19 2.51 1.69 1.64 0.61 10 H-LSL-10 -5.95
-2.58 0 57 3.22 2.6 1.77 2.03 9.45 E-LSL-10 -5.27 -1.42 35 0 3.39
2.56 1.94 2.17 3.32 Red 11 H-LSL-11 -6.30 -2.32 0 65 3.69 2.59 2.09
3.41 3.65 E-LSL-11 -5.19 -1.35 42 0 3.78 2.69 2.21 2.27 9.51 12
H-LSL-12 -6.13 -2.68 0 0 3.53 2.6 1.87 2.79 3.92 E-LSL-12 -5.20
-1.74 54 0 3.54 2.84 2.03 1.86 3.96 13 H-LSL-13 -6.28 -2.20 0 72
3.66 2.94 1.92 2.52 2.45 E-LSL-13 -5.23 -1.31 57 0 3.21 2.87 1.95
3.59 4.59 14 H-LSL-14 -5.87 -2.38 0 58 3.31 2.69 2.08 1.84 0.57
E-LSL-14 -5.11 -1.59 0 0 3.88 2.78 1.87 4.12 5.91 15 H-LSL-15 -5.93
-2.39 0 62 3.07 2.63 1.96 2.39 4.19 E-LSL-15 -5.29 -1.37 58 0 3.69
2.62 1.93 2.11 7.33 E-LSL (Compound A) -5.00 -1.25 0 0 3.23 2.50
2.76 2.96 0.01 H-LSL (Compound B) -6.03 -1.53 0 0 3.86 2.75 1.91
3.05 2.04 Blue-Host (NNA) -5.45 -1.95 -- -- 3.21 1.78 1.78 4.52
0.17 Green-Host (DPDDC) -5.55 -2.43 -- -- 2.69 2.75 1.98 4.12 2.84
Red-Host (BBCQ) -5.49 -2.24 -- -- 2.78 2.25 1.86 3.72 3.70
[0167] In such a case, structures of respective compounds used in
Table 1 of the present invention are as follows.
##STR00004## ##STR00005## ##STR00006## ##STR00007## ##STR00008##
##STR00009## ##STR00010## ##STR00011##
[Embodiments 1 to 5] Manufacturing of Blue Organic EL Devices
[0168] After respective compounds were subjected to high purity
sublimation purification by a conventionally known method, blue
organic EL devices were manufactured as follows.
[0169] First, a glass substrate thin-film-coated with indium tin
oxide (ITO) to a thickness of 1500 .ANG. was washed with distilled
water ultrasonically. After washing with distilled water was
completed, the glass substrate was ultrasonically cleaned with a
solvent, such as isopropyl alcohol, acetone and methanol, dried,
transferred to a UV OZONE cleaner (Power sonic 405, Hwasin Tech)
cleaned for 5 minutes using UV, and then transferred to a vacuum
evaporator.
[0170] On the ITO transparent electrode prepared as above, DS-205
(Doosan Electronics CO. LTD., 80 nm)/TCTA
(15)/E-LSL-1.about.E-LSL-5 (5 nm) D NNA+5% DS-405 (Doosan
Electronics CO. LTD., 3 nm)/H-LSL-1.about.H-LSL-5 (5 nm)/TNPT (25
nm)/LiF (1 nm)/Al (200 nm) were stacked in the order, and thus
organic EL devices were prepared.
TABLE-US-00002 TABLE 2 Thickness Compound (nm) Hole injection layer
DS-205 80 Hole transporting layer TCTA 15 E-LSL E-LSL-1~E-LSL-5 5
Light emitting layer NNA + 5% DS-405 30 H-LSL H-LSL-1~H-LSL-5 5
Electron transporting layer TNPT 25 Electron injection layer LiF 1
Cathode Al 200
[Comparative Example 1] Manufacturing of Blue Organic EL Device
[0171] A blue organic EL device of Comparative Example 1 was
manufactured in the same manner as in Embodiment 1, except that
Compound A was used as a material for the electron-leakage
suppression layer and Compound B was used as a material for the
hole-leakage suppression layer.
[0172] For reference, structures of TCTA, NNA, TNPT, Compound A,
and Compound B used in Embodiments 1 to 5 are as follows.
##STR00012## ##STR00013##
Evaluation Example 1
[0173] For each of the organic EL devices manufactured in
Embodiments 1 to 5 and Comparative Example 1, a driving voltage and
a current efficiency at a current density of 10 mA/cm.sup.2 were
measured and the results are shown in Table 3 below.
TABLE-US-00003 TABLE 3 Driving Current voltage efficiency
Embodiment E-LSL H-LSL (V) (cd/A) Embodiment 1 E-LSL-1 H-LSL-1 3.69
8.1 Embodiment 2 E-LSL-2 H-LSL-2 3.92 7.5 Embodiment 3 E-LSL-3
H-LSL-3 3.72 8.5 Embodiment 4 E-LSL-4 H-LSL-4 3.97 7.6 Embodiment 5
E-LSL-5 H-LSL-5 3.74 8.0 Comp. example1 Compound A Compound B 4.21
6.7
[0174] As shown in Table 3, it was appreciated that the organic EL
devices of Embodiments 1 to 5 that include, in the hole
transporting area and the electron transporting area, the
electron-leakage suppression layer and the hole-leakage suppression
layer, adjusted to have predetermined physical properties,
exhibited excellent performance in terms of the current efficiency
and driving voltage, as compared with the blue organic EL device of
Comparative Example 1.
[Embodiments 6 to 10] Manufacturing of Green Organic EL Device
[0175] After each compound was subjected to high purity sublimation
purification by a conventionally known method, green organic EL
devices were manufactured as follows.
[0176] First, a glass substrate thin-film-coated with indium tin
oxide (ITO) to a thickness of 1500 .ANG. was washed with distilled
water ultrasonically. After washing with distilled water was
completed, the glass substrate was ultrasonically cleaned with a
solvent, such as isopropyl alcohol, acetone and methanol, dried,
transferred to a UV OZONE cleaner (Power sonic 405, Hwasin Tech)
cleaned for 5 minutes using UV, and then transferred to a vacuum
evaporator.
[0177] On the ITO transparent electrode prepared as above, m-MTDATA
(60 nm)/TCTA (80 nm)/E-LSL-6.about.E-LSLS-10 (10 nm)/DPDDC+10%
Ir(ppy).sub.3 (300 nm)/H-LSL-6.about.H-LSL-10 (10 nm)/TNPT (30
nm)/LiF (1 nm)/Al (200 nm) were stacked in the order, and thus
organic EL devices were prepared.
[0178] Structures of m-MTDATA, DPDDC and Ir(ppy).sub.3 are as
follows.
##STR00014##
[Comparative Example 2] Manufacturing of Green Organic EL
Device
[0179] A green organic EL device of Comparative Example 2 was
manufactured in the same manner as in Embodiment 6, except that
Compound A was used as a material for the electron-leakage
suppression layer and Compound B was used as a material for the
hole-leakage suppression layer.
Evaluation Example 2
[0180] For each of the green organic EL devices manufactured in
Embodiments 6 to 10 and Comparative Example 2, a driving voltage
and a current efficiency at a current density of 10 mA/cm.sup.2
were measured and the results are shown in Table 4 below.
TABLE-US-00004 TABLE 4 Driving Current voltage efficiency
Embodiment E-LSL H-LSL (V) (cd/A) Embodiment 6 E-LSL-6 H-LSL-6 4.07
135.8 Embodiment 7 E-LSL-7 H-LSL-7 4.28 120.7 Embodiment 8 E-LSL-8
H-LSL-8 4.06 133.3 Embodiment 9 E-LSL-9 H-LSL-9 4.21 124.7
Embodiment 10 E-LSL-10 H-LSL-10 4.12 129.5 Comp. example 2 Compound
A Compound B 4.53 96
[0181] As shown in Table 4, it was appreciated that the organic EL
devices of Embodiments 6 to 10 that include, in the hole
transporting area and the electron transporting area, the
electron-leakage suppression layer and the hole-leakage suppression
layer, adjusted to have predetermined physical properties,
exhibited excellent performance in terms of the current efficiency
and driving voltage, as compared with the green organic EL device
of Comparative Example 2.
[Embodiments 11 to 15] Manufacturing of Red Organic EL Device
[0182] After each compound was subjected to high purity sublimation
purification by a conventionally known method, green organic EL
devices were manufactured as follows.
[0183] First, a glass substrate thin-film-coated with indium tin
oxide (ITO) to a thickness of 1500 .ANG. was washed with distilled
water ultrasonically. After washing with distilled water was
completed, the glass substrate was ultrasonically cleaned with a
solvent, such as isopropyl alcohol, acetone and methanol, dried,
transferred to a UV OZONE cleaner (Power sonic 405, Hwasin Tech)
cleaned for 5 minutes using UV, and then transferred to a vacuum
evaporator.
[0184] On the ITO transparent electrode prepared as above, m-MTDATA
(60 nm)/TCTA (80 nm)/E-LSL-11.about.E-LSLS-15 (10 nm)/BBCQ+ 10%
(piq).sub.2Ir(acac) (300 nm)/H-LSL-11.about.H-LSL-15 (10 nm)/TNPT
(30 nm)/LiF (1 nm)/Al (200 nm) were stacked in the order, and thus
organic EL devices were prepared.
[Comparative Example 3] Manufacturing of Red Organic EL Device
[0185] A red organic EL device of Comparative Example 3 was
manufactured in the same manner as in Embodiment 11, except that
Compound A was used as a material for the electron-leakage
suppression layer and Compound B was used as a material for the
hole-leakage suppression layer.
[0186] Structures of BBCQ and (piq).sub.2Ir(acac) used in
Embodiments 11 to 15 and Comparative Example 3 are as follows.
##STR00015##
Evaluation Example 3
[0187] For each of the red organic EL devices manufactured in
Embodiments 11 to 15 and Comparative Example 3, a driving voltage
and a current efficiency at a current density of 10 mA/cm.sup.2
were measured and the results are shown in Table 5 below.
TABLE-US-00005 TABLE 5 Driving Current voltage efficiency
Embodiment E-LSL H-LSL (V) (cd/A) Embodiment 11 E-LSL-11 H-LSL-11
3.96 38.6 Embodiment 12 E-LSL-12 H-LSL-12 4.19 32.4 Embodiment 13
E-LSL-13 H-LSL-13 3.94 39.2 Embodiment 14 E-LSL-14 H-LSL-14 4.12
33.2 Embodiment 15 E-LSL-15 H-LSL-15 4.01 38.1 Comp. example 3
Compound A Compound B 4.67 29
[0188] As shown in Table 5, it was appreciated that the organic EL
devices of Embodiments 11 to 15 that include, in the hole
transporting area and the electron transporting area, the
electron-leakage suppression layer and the hole-leakage suppression
layer, adjusted to have predetermined physical properties,
exhibited excellent performance in terms of the current efficiency
and driving voltage, as compared with the red organic EL device of
Comparative Example 3.
REFERENCE SIGNS
[0189] 100: Organic electroluminescent device [0190] A: Organic
layer [0191] 10: Anode [0192] 20: Cathode [0193] 30: Hole
transporting area [0194] 31: Hole injection layer [0195] 32: Hole
transporting layer [0196] 33: Electron-leakage suppression layer
[0197] 40: Light emitting layer [0198] 50: Electron transporting
area [0199] 51: Electron injection layer [0200] 52: Electron
transporting layer [0201] 53: Hole-leakage suppression layer
* * * * *